Attempt to fix flaky test in `user_views_iteration_spec.rb`

Attempts to fix the flaky test by adding `wait_for_requests`
to wait for a REST API call then a GraphQL API call.

https://gitlab.com/gitlab-org/gitlab/-/issues/323731

ee/spec/features/groups/iterations/user_views_iteration_spec.rb

@@ -81,7 +81,7 @@ RSpec.describe 'User views iteration' do
       end
     end
 
-    context 'when grouping by label', quarantine: 'https://gitlab.com/gitlab-org/gitlab/-/issues/323731' do
+    context 'when grouping by label' do
       before do
         sign_in(user)
 

ee/spec/features/projects/iterations/user_views_iteration_spec.rb

@@ -64,7 +64,7 @@ RSpec.describe 'User views iteration' do
 
     it_behaves_like 'render iteration page'
 
-    context 'when grouping by label', quarantine: 'https://gitlab.com/gitlab-org/gitlab/-/issues/323731' do
+    context 'when grouping by label' do
       it_behaves_like 'iteration report group by label'
     end
 

ee/spec/support/shared_examples/features/iteration_report_group_by_label_shared_examples.rb

@@ -6,8 +6,10 @@ RSpec.shared_examples 'iteration report group by label' do
 
     # Select label `label1` from the labels dropdown picker
     click_button 'Label'
+    wait_for_requests
     click_link label1.title
     send_keys(:escape)
+    wait_for_requests
   end
 
   it 'groups by label', :aggregate_failures do